I hit the accelerator hard and the car jumps ahead, but there is no roar of the engine. This is the new Ford Focus Electric with only a silent electric motor and the tremendous torque that provides for takeoff.

Ford’s entry in the electric car derby goes on sale next month to compete with the Nissan Leaf and the Chevrolet Volt (which also has a backup gasoline engine). Originally it will be sold only in green-car hotbeds of California, New York and New Jersey but will expand to another 16 markets by the end of 2012. I got a chance to test drive the Focus Electric at an event in New

York last week.

The kind of lead-foot acceleration I was trying out is not, however, how Ford or the car itself encourages you to drive. By driving gently and braking carefully, you help preserve and slightly increase the charge you need to get where you are going and back. Executives say the car has a range of 77 miles before needing a plug-in charge. On this day, that would have been no problem. A couple of taps on the navigation screen showed five Manhattan charging stations within a one-mile radius, mostly in parking garages. Here are some other impressions:

The dashboard constantly encourages you to drive for energy efficiency. Once you have set your destination into the navigation system, the car constantly measures how you are doing in keeping up sufficient charge. If you have a surplus, butterfly icons show up on the dashboard. When you brake the car, a battery icon flashes a percentage number to show how much of the energy you captured from the regenerative braking that helps recharge the battery.

It’s not complicated. Those specialized brakes are very sensitive. But after one too-quick stop, it is easy to change to slow, steady braking that gives maximum recharge. The navigation system and the controls for music and cell phone connections are the same as in any well-equipped gasoline Focus.

The car recharges pretty quickly. I didn’t get to try this feature, but Ford executives say a full recharge will take only three to four hours if you have a special 240-volt home charging station or find a similar public station. Ford is boasting that amounts to about half the full-charge time of the Nissan Leaf. On the other hand, if you just plug the Focus Electric into a 110-volt wall socket using the built-in charger, it will take 18 to 20 hours.

Why electrics cost so much

The big issue in selling the Focus, as with all current electric cars, is the high cost. The list price is $39,200 plus $1,499 for the necessary home charger. Against that, you can get a $7,500 federal tax credit and additional tax breaks in some states. One big reason why the price is so high became clearer last week. Ford CEO Alan Mulally said in a California speech that the batteries for the Focus Electric cost between $12,000 and $15,000, a figure not previously released.

The Focus Electric MPG figures are impressive. In a formula the EPA has developed to show numbers equivalent to gas mileage for electrics (expressed as MPGe), the Focus gets ratings of 110 MPGe in city driving, 99 on the highway and 105 MPGe combined. With similar high numbers, a recent study by the Union of Concerned Scientists says that an electric car owner could save between $750 and $1,200 a year compared with buying gas at $3.50 a gallon depending on electricity costs where the owner lived.

But that would take a very, very long time to make up the difference between the cost of a Focus Electric and the well-reviewed gasoline Focus selling for between $17,300 and $24,000, depending on the equipment. Some regular Focus models are rated for 40 MPG in highway driving.

How green are they?

Even the environmental advantage for electrics of emitting fewer climate-changing greenhouse gases isn’t always clear depending on how the electricity for your car’s charge is generated. The same Union of Concerned Scientists study sets out a map of where electrics have an advantage. In Seattle, which has lots of hydroelectric power, an electric car is responsible for only as much carbon dioxide emissions as a hypothetical, not yet in existence gasoline car with combined MPG ratings of 73. But in Colorado, with mostly coal-fired generation, an electric is responsible for more emissions – the equivalent of a gas car with a combined rating of 33 MPG like the current compact Mazda 3.

With Chevrolet Volt just now resuming production after a hiatus because of slow sales, the market for electric cars is unlikely to take off despite government incentives. Michael Omotoso, power train forecaster for LMC Automotive, projects that even by 2017, market share will be only 1.6% for a combination of all-electric cars and plug-ins with a gasoline motor (where he classifies the Volt).

But if you are a well-to-do, environmentally-minded buyer who does mostly short-run commuting and doesn’t mind monitoring your car constantly to make sure your battery is well-charged, the Focus Electric seems like a choice worth considering.